The present invention relates to an improved apparatus and process for cooling and de-steaming calcined gypsum stucco (calcium sulfate hemihydrate). The cooling of gypsum stucco has been of interest in the gypsum industry for many decades. Stucco is physically and thermodynamically unstable at high temperatures. In order to maintain its quality, the stucco should be quickly aerated and cooled below the temperature of calcination (250.degree. F.). This is especially true when the calcined stucco is to be stored over time.
Hot and steamy calcined stucco stored in containers will age over time. This aging process adversely affects many of the desirable properties of the stucco, including pouring consistency, hydration rate, set time, response to accelerator, and potential for strength development. If a storage silo does not empty its contents on a "first-in-first-out" basis, the quality of the stucco removed from storage can vary drastically. Thus, the cooling and de-steaming of calcined stucco before storage is essential to long-term age stability.
Apart from age stability during storage, a further problem is caused by mechanical energy from tube mill grinding during the processing of the stucco. The mechanical energy adds more heat to the stucco, preventing many plants from being able to meet temperature requirements for bagging the stucco. Thus, immediate cooling and de-steaming of hot calcined stucco allows for stucco to be properly bagged. that is required to cool the stucco. Expensive high volume blower equipment is required for such a system.
It is therefore an object of the present invention to provide an upright, compact apparatus for cooling and de-steaming stucco without the large space and high energy requirements of the prior cooling apparatus.
It is also an object of the present invention to provide an apparatus and process for cooling and de-steaming stucco that exhibits higher heat transfer coefficients than prior art cooling apparatus and processes.
It is a further object of the present invention to provide an apparatus for cooling and de-steaming stucco requiring lower pressure, lower capacity and less expensive blower equipment.
These and other objects will become readily apparent after reading the disclosure of the present invention herein.